Special Issue "ZnO and TiO2 Based Nanostructures"
A special issue of Nanomaterials (ISSN 2079-4991).
Deadline for manuscript submissions: closed (30 September 2017)
Transition-metal oxide nanostructures are the focus of current research efforts in nanotechnology since they are the most common minerals on Earth, and also thanks to their special shapes, compositions, and chemical and physical properties. They have now been widely used in the design of energy saving and harvesting devices, such as lithium-ion batteries, fuel cells, solar cells, and even transistors, light emitting devices (LEDs), hydrogen production by water photolysis and its storage, water and air purification by degradation of organic/inorganic pollutants, bio-sensing devices, environmental monitoring by their applications in the fabrication of gas, humidity, and temperature sensors, and photodetectors.
In addition to the great application potentials, oxide-based nanomaterials, such as ZnO and TiO2, have recently revolutionized nanomaterial research thanks to their outstanding properties. They can be produced in different shapes (such as nanowires, nanobelts, nanorods, nanotubes, nanocombs, nanorings, nanohelixes/nanosprings, nanocages and nanosheets, and nanostars) depending on the synthesis routes, which range in techniques.
This Special Issue of Nanomaterials will attempt to cover the most recent advances in ZnO and TiO2 nanostructures, concerning, not only the synthesis and characterization, but especially reports of their functional and smart properties to be applied in working devices. Applications of nanosized ZnO and TiO2 can range widely, from biomedical and drug delivery devices to piezoelectric and chemical sensors, and energy harvesting, conversion and storage devices.
Dr. Andrea Lamberti
Manuscript Submission Information
Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.
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- Advanced synthesis
- Smart properties
- Multifunctional materials
- Energy harvesting/storage device
- Bio-materials and bio-devices
The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.
Type of paper: Full paper
Tentative title: Time- and concentration-dependent evaluation of lipid-coated zinc oxide nanocrystals as photodynamic therapeutics in cancer cells
Short abstract: In the present paper we use zinc oxide nanocrystalline particles under the excitation of ultraviolet light for the generation of highly cytotoxic reactive oxygen species, with the aim of fighting cancer cells in vitro. Owing to the difficulties in obtaining highly dispersed nanocrystals (NCs) in biological media, we propose their coating with a double-lipidic bilayer and we evaluate their colloidal stability, cell internalization and cytotoxic behaviour in comparison to the bare zinc oxide NCs. By systematically varying the concentration of NCs and the application time of ultraviolet light, we measure the type and amount of generated reactive oxygen species (ROS) by Electron Paramagnetic Resonance (EPR) spectroscopy. We finally evaluate the cytotoxic effect toward HeLa Cancer cells, showing promising results for the development of potential ZnO-based therapeutic systems.
Article Type: Review
Title: Engineering the Surface/Interface Structures of Titanium Dioxide Micro/Nano Architectures towards Environmental and Electrochemical Applications
Authors: Xiaoliang Wang 1,*, Yanyan Zhao 2 and Hongyu Sun 3,*
Affiliation: 1 College of Science, Hebei University of Science and Technology, Shijiazhuang 050018, PR China; firstname.lastname@example.org (X. W.)
2 Department of Chemistry Boston College Merkert Chemistry Center, 2609 Beacon St., Chestnut Hill, Massachusetts 02467, USA; email@example.com (Y. Z.)
3 Department of Micro- and Nanotechnology, Technical University of Denmark, Kongens Lyngby 2800, Denmark; firstname.lastname@example.org (H. S.)
Correspondence: email@example.com; firstname.lastname@example.org; Tel.: +45-45 25 68 40 (H. S.)
Abstract: Titanium Dioxide (TiO2) micro/nano architectures have been intensively studied in the past years because of the applications in environmental, energy conversion, and storage fields, such as heterogeneous catalysis, dye-sensitized solar cells, lithium/sodium ion batteries, lithium sulfur batteries, sensors, bio-nanotechnology, etc. Surface and/or interface structures in the TiO2 micro/nano architectures play important roles in those applications. This mini review article focuses on TiO2 micro/nano architectures with typical crystal structures (anatase, rutile, brookite, and TiO2(B)), and summarizes major advances in the surface/interface engineering, characterization, applications in environment and electrochemical devices. We present the principles and growth mechanisms of TiO2 nanostructures via different methods, with an emphasis on rational control of the surface and interface structures. We next discuss the applications of TiO2 micro/nano architectures in photocatalytic degradation of organic contaminants in water, electrochemical sensor, lithium/sodium ion batteries, and lithium sulfur batteries. Throughout the discussion, the relationship between the device performance and the surface/interface structures of TiO2 micro/nano structures will be highlighted. Then we discuss the phase transitions of TiO2 nanostructures and possible strategies of improving the phase stability. This review concludes with a personal perspective on the current challenges and future researches.
Keywords: titanium oxide; crystal structure; surface/interface structures; photocatalytic degradation; sensor; lithium ion battery
Title: Photocatalytic properties of zinc oxide hierarchical structures electrodeposited on metallic web electrodes
Authors: Elena Matei, Cristina Busuioc, Mihaela Oancea, Alexandru Evanghelidis, Camelia Florica, Monica Enculescu, Ionut Enculescu*
*Corresponding author: email@example.com
National Institute for Materials Physics, Magurele, Ilfov, Romania, RO-077125
Abstract: Metallic web electrodes were prepared by electrospinning poly(methyl methacrylate) fibers onto metal frame collectors and subsequent metallization by DC sputtering. These were thermally transferred onto glass substrates and employed as working electrodes for the electrochemical deposition of ZnO. The transparency of the webs, a function of fiber density, is comparable to that of conventional transparent conductive oxides.
Figure 1. The steps in preparing the substrates for ZnO electrodeposition: (a) as-spun PMMA web, (b) gold covered web, (c) glass substrate covered with the metallic web electrode (the two gold stripes were sputtered on glass for a better clamping contact when performing the electrodeposition) and (d) microscopic detail of the metal covered PMMA web.
As well, the same enhanced control of the ZnO electroplating process was observed for the case of using web electrodes as for performing deposition on transparent conducting oxides or on metal substrates electrodes. Structural, optical and morphological properties were investigated and correlated to the electrodeposition conditions. Such hierarchically structured electrodes can be employed in a wide range of applications where flexible transparent conducting layers are required.
Figure 2. SEM images of ZnO nanorods deposited on metallic web electrodes from bath containing 0.5 mM Zn(NO3)2 and 100 mM KNO3
One example of such application is related to the photocatalytic activity of ZnO coated fibers. This was analyzed by studying the photodegradation of methylene blue films under UV irradiation.
Title: In Vitro Sonodynamic Therapeutic Effect of Polyion Complex Micelles Incorporating Titanium Dioxide Nanoparticles
Authors: Satoshi Yamamoto, Masafumi Ono, Eiji Yuba, Atsushi Harada* and Kenji Kono
Abstract: Titanium dioxide nanoparticles (TiO2 NPs) has available ability to act as a sonosensitizer, which can generate reactive oxygen species by ultrasound irradiation, for sonodynamic therapy. For the delivery of TiO2 NPs, we prepared polyion complex micelles incorporating TiO2 NPs (TiO2 NPs-PIC micelles) by mixing TiO2 NPs and polyallylamine bearing poly(ethylene glycol) grafts. In this study, the effect of polymer composition and ultrasound irradiation condition to sonodynamic therapeutic effect toward HeLa cells were evaluated through the experiments including the evaluation of cell viability, the observation of intracellular distribution and cell staining assay. TiO2 NPs-PIC micelles with widely-distributed feature induced a significant decrease in cell viability by ultrasound irradiation. Also, the prolongation of irradiation time provided more effective cell-killing compared with an increase in ultrasound power. Further, it was confirmed that the combination of TiO2 NPs-PIC micelles and ultrasound irradiation induced apoptotic cell death.
Title: ZnO nanowire synthesis and application in sensing
Author: Guido Viscardi
Abstract: This article will provide a comprehensive review of the state-of-the-art research activities focused on the advanced synthesis and application of ZnO nanowires (NWs) for sensing. In the beginning synthesis methods are briefly introduced, namely hydrothermal and vapor phase methods, demonstrating approaches for controlled synthesis of different ZnO NW morphology and further methods for ZnO NW surface modification, discussing how this effects the sensing. Next, UV and gas sensing mechanisms are briefly discussed, sensor types: single nanowire, nanowire junction (or Schottky contact) and p-n junction sensors are described. Further, novel approaches for sensing, using ZnO NW hybrid structures with other materials, such as metal nanoparticles or carbon nanomaterials will be demonstrated, limiting factors and possible improvement will be discussed . The review will then conclude with some perspectives and outlook on the future developments in the ZnO NW application for sensing.
Title: Resistive Switching of 5 nm TiO2 Nanoparticle Self-Assembled Monolayers
Authors: Dirk Oliver Schmidt 1,2, Nicolas Raab 3,4, Michael Noyong 1,2, Venugopal Santhanam 5, R. Dittmann 3,4 and Ulrich Simon 1,2,*
Affiliations: 1 JARA-FIT, 52056 Aachen, Germany; firstname.lastname@example.org
2 Institute of Inorganic Chemistry, RWTH Aachen University, 52074 Aachen, Germany; email@example.com
3 JARA-FIT, 52425 Jülich, Germany; firstname.lastname@example.org
4 Peter Grünberg Institut 7, Forschungszentrum Jülich GmbH, Jülich, 52428, Germany; email@example.com
5 Department of Chemical Engineering, Indian Institute of Science, Bangalore, India-560012; firstname.lastname@example.org
Correspondance: email@example.com; Tel.: +49-241-80-94644
Abstract: Resistively switching devices are promising candidates for the next generation of non-volatile data memories. Such devices are up to now fabricated mainly by means of top-down approaches applying thin films sandwiched between electrodes. Recent works have demonstrated that resistive switching (RS) gets feasible also on chemically synthesized nanoparticles (NPs) in the 50 nm range. By following this concept, we developed this approach further to the sub-10 nm range. In this work, we report RS of 5 nm TiO2 NPs that were self-assembled into monolayers and transferred on metallic substrates. We electrically characterized these monolayers in regard to their RS properties by means of a nanorobotics system in a scanning electron microscope and found typical features of bipolar resistive switching.
Title: Soft synthesis of N-doped yellow anatase nanoparticles
Authors: David G. Calatayud1, Raquel M. Flores1,2, Amador C. Caballero1, Teresa Jardiel1
Affiliation: 1 Department of Electroceramics, Instituto de Cerámica y Vidrio – CSIC, Kelsen 5, Campus de Cantoblanco, 28049, Madrid, Spain
2 Universidad Rey Juan Carlos, Avda. de Atenas, s/n 28922 Alcorcón, Madrid
Abstract: Titanium dioxide has become a material of great interest, both form a scientific and technological point of view, due to its excellent optical and electronic properties, a strong oxidising power, chemical stability and low toxicity. These characteristics make it a good candidate to be used in various fields, among which is the photocatalysis. In this sense, the properties of TiO2 can be modulated through precise control of crystallinity, crystalline phase, shape and size of the particles together with the band-gap engineering. In this work, nanoparticles with controlled size and crystallinity have been synthesized using a solvothermal process under different reaction conditions and urea as a doping agent. N-doped yellow pure anatase nanoparticles have been obtained with a reduce band gap (< 3.0 eV), increasing the light absorption range of TiO2 nanoparticles. In addition, this synthetic method allows a high incorporation of N into the material using soft conditions and low temperature.
Title: Crystallization of TiO2 nanotubes by in situ heating TEM
Authors: Alberto Casu 1, Andrea Lamberti 2, Stefano Stassi 2, and Andrea Falqui 1,*
1 King Abdullah University of Science and Technology (KAUST), Biological and Environmental Sciences and Engineering (BESE) Division, NABLA Lab, 23955-6900 Thuwal, Saudi Arabia
2 Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy
Abstract: The thermally-induced crystallization of TiO2 amorphous nanotubes so far has been studied under standard pressure conditions by techniques such as differential scanning calorimetry and in situ X-Ray diffraction, then looking at the overall response of several thousands of nanotubes. Here we report a study of this phenomenon based on an in situ transmission electron microscopy approach that uses a twofold strategy. First, a group of some tens of TiO2 amorphous nanotubes was heated looking at their electron diffraction pattern change versus temperature, in order to determine both the initial temperature of crystallization and the corresponding crystalline phases. Second, the experiment was repeated on groups of few nanotubes, directly imaging their structural evolution in the direct space by spherical aberration-corrected high resolution transmission electron microscopy. These studies showed that, differently from what happens under standard pressure conditions, under the microscope's high vacuum the crystallization of TiO2 amorphous nanotubes starts from local small seeds of rutile and brookite, which then grow up with the increasing temperature. Besides, the crystallization started at different temperatures when the in situ heating was performed irradiating the sample with an electron beam energy of 120 or 300 keV, being such temperatures 450 °C and 380 °C, respectively. This difference is due to atomic knock-on effects induced by the electron beam with diverse energy.
Title: Thermally stimulated currents in nanocrystalline titanium dioxide
Authors: Mara Bruzzi 1,*, Riccardo Mori 2, Ennio Carnevale 3, Monica Scaringella 4, and Franco Bogani 3
1 Dipartimento di Fisica e Astronomia, Università di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, Firenze, Italy
2 Albert-Ludwigs-Universität Freiburg, Experimentelle Teilchenphysik, Physikalisches Institut, Hermann-Herder Straße 3, 79104 Freiburg im Breisgau, Germany
3 Dipartimento di Ingegneria Industriale, Università di Firenze, Via S. Marta 1, 50139 Firenze, Italy
Abstract: A set of nanocrystalline TiO2 (nc-TiO2) films have been deposited on thick-alumina printed circuit boards equipped with electrical contacts, heater and temperature sensors, in view to perform a detailed thermally stimulated currents (TSC) analysis in a broad temperature range. Fractional TSC spectra in the temperature range 5-300K have been measured after illuminating the sample with a UV led at liquid He temperature. Data have been processed by means of a numerical simulation considering both free and localized carrier contributions. The numerical procedure takes into account of a density of states (DOS) characterized by an exponential tail of localized states joined to a parabolic density of extended states. Results show that hopping gives the main contribution to electrical conduction, with a density of defect states around 10^20cm-3 and an exponential band-tail energy constant around 50 meV. TSC analysis has been also carried out in the temperature range 300-625K after storage in selected controlled atmosphere conditions, to elucidate the role of adsorbed water vapour molecules and of vacancy-oxygen defects to the conduction mechanisms.